Method for shaping pole pieces of magnetic heads by chemical mechanical polishing

ABSTRACT

A thin film magnetic head that includes an improved P 2  pole tip/yoke interface. The process for forming the P 2  pole tip/yoke interface includes a CMP polishing step that is performed on the surface of the wafer subsequent to the plating of the P 2  pole tip. This CMP step utilizes a relatively soft polishing pad and an acidic polishing slurry which preferentially attacks the P 2  pole tip material, such that the CMP step results in the recession of the upper surface of the P 2  pole tip relative to the dielectric layer surrounding it, as well as the significant rounding of the upper edges of the dielectric trench in which the P 2  pole tip is formed. Thereafter, when the yoke is plated onto the P 2  pole tip the rounded upper edges of the dielectric trench result in a concave curved interface between the yoke and the P 2  pole tip.

CROSS REFERENCE TO RELATED APPLICATION

The present invention is a divisional application of Ser. No.09/948,957, filed Sep. 7, 2001, now U.S. Pat. No. 6,912,772, which is adivisional application of Ser. No. 09/504,969, filed 02/15/2000, nowU.S. Pat. No. 6,510,022.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to thin film magnetic heads andmethods for manufacturing such heads, and more particularly to thefeatures of the P2 pole tip/yoke interface of thin film magnetic writehead elements and methods for manufacturing the P2 pole tip/yokeinterface.

2. Description of the Prior Art

The well known basic components of thin film magnetic write headsinclude a first pole (P1), a write gap layer, a narrow P2 pole tip, ayoke that is electromagnetically engaged with the P2 pole tip, andelectromagnetic coils that generate a magnetic flux that flows betweenthe P1 pole and the P2 pole tip. The width of the P2 pole tip generallydefines the track width of the data bits written by the write head. Theyoke is generally significantly wider and thicker than the P2 pole tipand it serves to control and focus the flow of magnetic flux generatedby the electromagnetic coils of the write head into the P2 pole tip. Theflow of magnetic flux between the P1 pole and the P2 pole tip across thewrite gap influences the magnetic media disposed proximate the writehead to record flux changes therein as data bits. Thus, a significantperformance characteristic of write heads is the proper controlled flowof magnetic flux from the yoke into the P2 pole tip and across the writegap. Where the magnetic flux flow control is faulty, the magnetic fluxcan flow directly from the yoke to the P1 pole without passing throughthe P2 pole tip. This undesirable effect is termed “side writing” as itcreates an undesirable noise band on each side of the data track that iswritten by the P2 pole tip, and the existence and width of theundesirable side band affects the spacing between the data tracks. Whereside writing is minimized, such that the width of the side bands isminimized, data tracks can be written closer together such that moretracks per inch (TPI) can be written and the areal data storage of themagnetic media can be increased.

In prior art pole tips of various designs, the P2 pole tip/yokeinterface is characterized as a “T” interface. That is, the P2 pole tipis the downward leg of the “T” and the yoke is formed flatly andsquarely on top of the P2 pole tip leg. Thus the inner angle between theP2 pole tip and the yoke is approximately a right angle. This rightangle P2 pole tip/yoke interface results in less than optimum magneticflux flow control between the yoke and the P2 pole tip. That is, flow ofmagnetic flux is somewhat inhibited at the right angle interface, andthis can result in side writing when the magnetic flux flows directlyfrom the yoke to the P1 pole, rather than flowing through the P2 poletip. It is therefore possible to improve the flow of magnetic fluxthrough the P2 pole tip/yoke interface and thus reduce side writing byshaping the interface to remove the right angle joinder of the yoke tothe P2 pole tip. The present invention is a write head that includessuch an improved P2 pole tip/yoke interface, together with a process formanufacturing it.

SUMMARY OF THE INVENTION

The thin film magnetic head of the present invention includes animproved P2 pole tip/yoke interface structure. The interface structureincludes yoke material that is formed in a concave curved shape at theinterface between the P2 pole tip and the yoke, such that a right angleinterface between the P2 pole tip and the yoke is eliminated.

The process for forming the P2 pole tip/yoke interface includes a secondCMP polishing step that is performed on the surface of the write headwafer subsequent to the plating of the P2 pole tip thereon, andsubsequent to a first CMP step. This second CMP step utilizes arelatively soft polishing pad and an acidic polishing slurry having a pHwithin the range of approximately 1 to approximately 5, and preferablyapproximately 2.5. The acidic polishing slurry contains a chemical agentwhich preferentially attacks the P2 pole tip material, such that thesecond CMP step results in the recession of the upper surface of the P2pole tip relative to the dielectric layer surrounding it, as well as thesignificant rounding of the upper edges of the dielectric trench inwhich the P2 pole tip is formed. Thereafter, when the yoke is platedonto the P2 pole tip the rounded upper edges of the dielectric trenchresult in a concave curved interface between the yoke and the P2 poletip.

The resulting P2 pole tip/yoke interface possesses improved magneticflux flow control properties and results in decreased side writing.Greater track per inch areal data storage results from the reduced sidewriting of the improved write head.

It is an advantage of the magnetic head of the present invention thatincreased areal data storage is obtained.

It is another advantage of the magnetic head of the present inventionthat reduced side writing from the write head is obtained.

It is a further advantage of the magnetic head of the present inventionthat data tracks on magnetic media can be written closer togetherbecause the side band noise created by side writing is reduced.

It is a yet another advantage of the magnetic head of the presentinvention that improved magnetic flux flow control through the P2 poletip/yolk interface is obtained.

It is an advantage of the process for manufacturing a magnetic head ofthe present invention that a second CMP polishing step on the write headperformed immediately following a first CMP polishing step results in amagnetic head having improved performance characteristics.

It is another advantage of the process for manufacturing a magnetic headof the present invention that a second CMP polishing step on the writehead following a first CMP polishing step adds little to themanufacturing time of the write head elements.

It is a further advantage of the process for manufacturing a magnetichead of the present invention that a second CMP polishing step followinga first CMP polishing step adds little to the manufacturing expense ofthe write head elements.

These and other features and advantages of the present invention willbecome better known and understood upon reading the following detaileddescription which makes reference to the several figures of thedrawings.

IN THE DRAWINGS

FIG. 1 is a side cross-sectional view presenting a schematicillustration of a portion of a thin film magnetic head disposed on awafer substrate as configured during a process step executed in themanufacturing thereof, as is known in the prior art;

FIGS. 2–8 depict the thin film magnetic write head elements of FIG. 1 insubsequent manufacturing process steps, as are known in the prior art;

FIG. 9 depicts a new process step of the present invention executed inthe manufacturing of the thin film magnetic write head elements of thepresent invention;

FIGS. 10–15 depict the thin film magnetic write head elements of FIG. 9in subsequent manufacturing process steps, as are known in the priorart;

FIG. 16 is a perspective view of the thin film magnetic head of thepresent invention including the improved P2 pole tip/yoke interfacethereof; and

FIG. 17 is a simplified top plan view of a hard disk drive including themagnetic head of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Methods for manufacturing magnetic heads involve many process steps, asare generally well known in the prior art, and FIGS. 1–8 and 10–15generally depict prior art process steps involved in depositing andremoving of layers of various materials upon the wafer surface, whichsteps ultimately result in the creation of a plurality of write headcomponents upon the wafer surface. The write head components aresubsequently separated and further processed to become discrete thinfilm magnetic write heads. It is important to note that not all writehead manufacturing process steps are described herein, but only thoseprocess steps deemed significant to the description and understanding ofthe present invention. Additionally, while the detailed descriptionherein is directed to thin film magnetic write head elements, it isintended that the invention and claims herebelow include thin filmmagnetic heads that include read head components in addition to thewrite head components described herein.

As is described in detail herebelow the new write head pole tip includesan improved P2 pole tip/yolk interface that has improved magnetic fluxcontrol properties which results in decreased side writing. This allowsfor an increase in the areal density of data storage on a disk byreducing the width of the noise band between adjacent data tracks, suchthat the number of tracks per inch (TPI) can be increased. A detaileddescription of the present invention is next provided.

FIG. 1 is a side cross sectional view presenting a schematicillustration of a portion of one of many write head components that arein the process of being manufactured upon a wafer substrate, and it willserve as the starting point for the description of the presentinvention. As depicted in FIG. 1, a first pole (P1) 14 has been formedon the wafer surface. Thereafter, a gap layer 18 has been deposited uponthe P1 pole tip, and a seed layer 22 has been deposited upon the gaplayer 18. The seed layer is generally composed of the same material as asubsequently deposited second pole tip material and serves to providegood adherence of the subsequently deposited P2 pole tip material.

In the next process step, as depicted in FIG. 2, a resist plating framelayer 26 is deposited upon the seed layer 22. Utilizing standardphotolithographic processing steps, a hole or trench 30 is formed in theresist layer 26 for the subsequent deposition (typically byelectroplating) of the second pole tip (P2) 34. Further openings 36 areformed in the resist plating frame layer 26, as is well known in theart. Thereafter, as depicted in FIG. 3, the material that forms the P2pole tip 34 is electroplated into the trench 30 typically to a thicknessless than the depth of the trench 30, so as to prevent mushrooming ofthe P2 pole tip and the openings 36 are also plated up with the material38. The P2 pole tip 34 may be composed of various materials as are knownin the art, with a nickel iron (NiFe) composition being specifically,though not necessarily, used in the present invention. Thus the seedlayer 22 is also composed of NiFe.

Thereafter, as depicted in FIG. 4, the resist layer 26 is chemicallystripped, such that the P2 pole piece 34 the outer frame pieces 38 andthe seed layer 22 are exposed. Then, as depicted in FIG. 5, the P2 poletip and inner portions 40 of the seed layer 22 are covered by a shieldlayer 44, and a chemical etch process is undertaken to remove theexposed outer frame pieces 38 as well as portions of the seed layer 22.Thereafter, the shield layer 44 is removed and the inner portions 40 ofthe seed layer are then exposed, and the exposed inner seed layerportions 40 together with any remaining seed layer portions are removedutilizing a sputtering or ion milling tool. FIG. 6 depicts this stage inthe manufacturing process, wherein the P2 pole tip 34 and a portion 48of the seed layer immediately below the pole tip 34 are disposed uponthe gap layer 18. It is to be noted that the preceding process stepdescription is a generalization and well known in the prior art. Also,other and different process steps may be utilized to achieve theresulting configuration depicted in FIG. 6.

Next, as depicted in FIG. 7, a layer of a dielectric material 60 isdeposited on the wafer surface. The layer 60 is typically though notnecessarily formed of alumina, and upwardly projecting portions 64 ofthe alumina layer 60 are formed wherever projecting P2 pole tips areformed on the wafer. A first chemical mechanical polishing (CMP) step isnext conducted upon the wafer. The first CMP step utilizes a relativelyhard polishing pad and a chemical polishing slurry that removes aluminaand NiFe at approximately equal rates. The slurry may have a neutral pHwith a pasivating agent such as BTA (benzothiazole), to a higher pH ofapproximately 10 where a pasivating agent normally is not required. Achemical oxidant may be included in the slurry, and a preferred oxidantis ammonium persulfate. The relatively hard pad preferentially removesthe projecting portions 64 and the slurry attacks and remove the alumina60 and the NiFe that constitutes the P2 pole tip. The first CMP step isconducted until the top surface 68 of each P2 pole tips 34 formed on thewafer is exposed within the polished surface 72 of the alumina layer 60,as is depicted in FIG. 8.

All of the preceding process steps described hereabove and depicted inFIGS. 1 through 8 are known and practiced in the prior art write headpole tip manufacturing processes. They have been described herein toprovide a general background for understanding the following processsteps that comprise the novel features of the present invention.Specifically, the significant step of the present invention comprisesthe implementation of a second CMP processing step at this point in thepole tip manufacturing process, as is next described.

The second CMP step of the present invention involves the utilization ofa relatively soft polishing pad along with an acidic polishing slurry.An oxidant, such as ammonium persulfate is preferably included in theacidic polishing slurry. The acidic polishing slurry coupled with thesoft polishing pad of the second CMP step create an environment in whichthe P2 pole tip is preferentially attacked as compared to the alumina.As a result, as depicted in FIG. 9, the second CMP step acts to removethe upper surface 68 of the pole tip 34 to form a recessed P2 pole tipsurface 80. Additionally, the polishing action of the second CMP stepcauses a rounding of the upper edges 84 of the alumina 60 above thesurface 80 of the P2 pole tip 34. In the preferred embodiment, theacidic CMP polishing slurry preferably has a pH of from approximately 1to approximately 5 with a preferred pH of approximately 2.5. Generally,a more acidic polishing slurry will more rapidly attack the NiFe poletip material as compared to the alumina, and a polishing slurry having apH lower than approximately 3 will generally cease to significantlyremove alumina, whereas a slurry having a pH higher than approximately 5will remove excess alumina. Thus it is desirable to have a slurrychemistry including a pH that is appropriate to attack the NiFe at anacceptable rate while not attacking the alumina too greatly. Owing tothe small dimensions of the P2 pole tip, it is generally desirable thatthe CMP polishing action of the pole tip be conducted at least asrapidly as the chemical action of the acidic slurry upon the pole tip.Where it is necessary to slow the chemical attack of the acidic slurryupon the pole tip, an oxidation inhibitor such as benzothiazole (BTA)may preferentially be added to the acidic slurry to protect the P2 poletip from overreactive acid attack during the second CMP polishing stepof the present invention. The CMP polishing slurries described hereinare available from several commercial sources. One such source is TheCabot Corporation, located in Aurora, IL; the preferred acidic slurry ofthe second CMP step is designated as Semi Sperse W 2000.

Therefore, as depicted in FIG. 9, the result of the second CMP polishingstep of the present invention is that the upper surface 80 of the P2pole tip is recessed into the alumina 60, and the upper edges 84 of thealumina are rounded by the second CMP polishing step. The degree ofroundness of the edges 84 is somewhat a function of the width of the P2pole tip, and where a one micron width P2 pole tip has undergone thesecond CMP polishing step of the present invention, the pole tip surface80 is recessed approximately 0.3 microns and the rounded edges 84 of thealumina have a radius of curvature of approximately 0.3 microns.

Following the second CMP polishing step of the present invention theelectromagnetic coils of the write head are next formed utilizing manyprocess steps that are generally known and utilized in the prior art.These process steps are peripheral to the invention described herein andwill not be described in detail. Thereafter, the yoke portion of thewrite head is formed onto the P2 pole tip. Specifically, as depicted inFIG. 10, a second seed layer 90 is deposited upon the surface of thewafer. The seed layer 90 covers the upper surface 80 of the P2 pole tipand serves to provide good electromagnetic conduction between the yoke(to be formed) and the upper surface 80. Thereafter, as depicted in FIG.11, a resist layer 94 is deposited upon the seed layer 90 andphotolithographic steps are conducted to form a trench 98 into which theyoke will be plated. Thereafter, as depicted in FIG. 12, the yoke 104 iselectrochemically plated into the trench 98 of the resist layer 94.

Next, as depicted in FIG. 13, the resist layer 94 is removed to exposethe yoke 104 and the second seed layer 90. Thereafter, the exposed seedlayer 90 is removed utilizing process steps similar to those describedhereabove with regard to the first seed layer 22, as depicted in FIGS.4, 5 and 6. FIG. 14 depicts the device following the removal of theexposed seed layer 90, such that only the seed layer portions 108between the P2 pole tip 34 and the yoke 104 remain. Thereafter, asdepicted in FIG. 15, a further layer 120 of dielectric material such asalumina is deposited upon the wafer surface, which typically results inthe formation of projecting portions 124 of the alumina layer 120. Thecompleted write head 126, with a completed P2 pole tip/yoke interface128 of the present invention, is depicted in FIG. 15. The significantfeature of the P2 pole tip/yoke interface 128 of the present inventionis the curved surface 130 proximate the joinder of the P2 pole tip 34and the yoke 104. Specifically, the rounded upper edges 84 that arecreated in the second CMP step of the present invention result incorresponding concave rounded edges 130 of the yoke 104 at the interface128 between the P2 pole tip 34 and the yoke 104. These concave roundededges 130 of the present invention are to be contrasted with the rightangle interface between the P2 pole tip and the yoke as is found in theprior art “T” type P2 pole tips.

To provide a more complete understanding of the present invention anisometric view with cutaway portions of the dielectric layers (60 and120) of the completed write head 126 of the present invention ispresented in FIG. 16. As depicted therein, the air bearing surface (ABS)160 of the write head 126 includes the P1 pole 14, the gap layer 18, theremaining first seed layer 48, the P2 pole tip 34, the remaining secondseed layer 90 and the yoke 104. The concave curved surface 130 of the P2pole tip/yoke interface 128 appears on the ABS surface and is formedproximate all edges of the joinder between the P2 pole tip 34 and theyoke 104, including the side surfaces 164 of the P2 pole tip 34 and theinner rearward surface 168. The magnetic flux generated within the writehead 126 passes through the interface 128 between the yoke 104 and theP2 pole tip 34, such that the interface 128 is both the point ofphysical engagement and electromagnetic engagement of the yoke 104 withthe P2 pole tip 34. An advantage of the P2 pole tip/yoke interface 128of the present invention is that the magnetic flux from the yoke 104passes more efficiently into the pole tip 34 than in the prior art “T”type P2 pole tip/yoke interface configurations. Specifically, the sharpinterior right angle of the prior art “T” configuration inhibits theefficient magnetic flux conduction between the yoke and the P2 pole tip,and results in undesirable magnetic side writing through the unwantedflow of magnetic flux directly from the yoke 104 to the P1 pole 14,rather than the proper flow of magnetic flux from the yoke 104 throughthe P2 pole tip 34 to the P1 pole 14. The rounded concave surfaces 130of the P2 pole tip/yoke interface 128 of the present invention thereforecreate a more efficient write head that has reduced side writing,because the magnetic flux is more efficiently channeled into the P2 poletip 34 for the desired flux flow across the write gap layer 18 from theP2 pole tip 34 to the P1 pole 14.

A simplified top plan view of a disk drive 180 that includes a thin filmmagnetic head of the present invention is depicted in FIG. 17. The diskdrive 180 includes one or more hard disks 184 and one or more actuatorarms 188 that have a slider device 192 mounted thereto. A magnetic head126 of the present invention is formed on a surface of the slider memberutilizing the manufacturing techniques described hereabove. As is wellknown to those skilled in the art, the disk drive 180 includesadditional electromechanical and computerized components (not shown).

While the present invention has been shown and described with regard tocertain preferred embodiments, it will be understood by those skilled inthe art upon reading the preceding disclosure that certain alterationsand modifications in form and detail may be made therein. It istherefore intended by the inventors that the following claims cover allsuch alterations and modifications that nevertheless include the truespirit and scope of the invention.

1. A method for manufacturing a magnetic head upon a substratecomprising the steps of: forming a P1 magnetic writing pole layer;forming a gap layer upon said P1 pole layer; forming a P2 magneticwriting pole tip upon said gap layer, said P2 pole tip being disposedwithin a first dielectric layer; conducting a first polishing step uponsaid first dielectric layer to achieve a flat, coplanar surface of saidP2 pole tip and said first dielectric layer; conducting a secondpolishing step upon said first dielectric layer to achieve a recessed P2pole tip surface and convex rounded edges of said first dielectric layerproximate said P2 pole tip; forming a yoke member upon said P2 pole tip,said yoke member being formed with a concave curved surface located inpart on an ABS surface of the magnetic head, said concave curved surfacebeing formed upon said rounded edges of said first dielectric layer. 2.The method for manufacturing said magnetic head as described in claim 1wherein an acidic polishing slurry is utilized in said second polishingstep.
 3. The method for manufacturing said magnetic head as described inclaim 2 wherein said polishing slurry has a pH of from approximately 1to approximately
 5. 4. The method for manufacturing said magnetic headas described in claim 3 wherein said pH is approximately 2.5.
 5. Themethod for manufacturing said magnetic head as described in claim 3wherein a relatively soft polishing pad is utilized during said secondpolishing step.
 6. The method for manufacturing said magnetic head asdescribed in claim 1 wherein said rounded upper edges have a radius ofcurvature of approximately 0.3 microns.